Concrete block machines are used to fabricate concrete blocks, including for example, cinder blocks and keystone pavers. As depicted in FIG. 1, block machines typically include a compression head 16, a mold plunger 18 extending downward from a bottom side of the compression head and a mold box 22 situated below and alignable with the mold plunger. In use, concrete, which typically includes a damp mixture of cement, sand and aggregate, is deposited into the mold box 22 and the compression head pivoted downward bringing the plunger head 18 into engagement with the mold box for compressing the concrete into a style of blocks dictated by the corresponding arrangement of the plunger head and the mold box.
To control the movement of the compression head during its descent, that is, to minimize the amount of lateral or front to back movement of the compression head, the compression head is often associated with a set of guide rails 28. These guide rails are typically located adjacent to each of the four corners of the compression head and in parallel to the axis of descent of the compression head. Utilizing guide brackets 31 attached about the four corners of the compression head, the compression head's lateral and front to back movement is minimized as the guide brackets slideably engage the rails as the compression head descends. However, guide rails alone have proven to be inadequate at decreasing compression head play. Specifically, for example, the amount of undesired movement of the compression head of some existing block machines is approximately ¼ of an inch. In other words, the compression head of one of these machines is allowed to swing laterally and/or front to back a distance of about ¼ of an inch. The variance between the mold plunger and the mold box however can be less than 1/16 of an inch in many of these block machines. Consequently, it is not uncommon for the plunger head to strike the mold box where it was not intended to strike thereby damaging both the plunger head and the mold box, including the mold box end liner and mold box core. Additionally, overtime, the cylinders that actuate the compression head can be so damaged as to require replacement.